Beam Shaping Technique Based On Spatial Light Modulator

With the rapid development of laser applications,traditional Gaussian beam is challenging to satisfy the requirement of various applications due to its characteristics of fixed far-field spot,uneven energy distribution,and certain divergence angle.Shaping a Gaussian beam into a special optical field with specific intensity and phase distribution has attracted worldwide research attentions.Meanwhile,the commercialization of spatial light modulators(SLMs)has further promoted the development of beam shaping technique,for the ease of achieving a fine-tuning of light field.The thesis is focused on the liquid crystal SLM enabled complex beam shaping technique technology,in order to obtain the specially structured light field.The main research outcomes are summarized as follows,(1)We first introduce the operation principle of SLM based beam shaping,including the operation principle of phase-type liquid crystal spatial light modulator,complex amplitude manipulation technique and complex coding algorithm based on the grating diffraction theory.(2)We carry out numerical investigation on the generation of high-order Bessel beam,Laguerre-Gaussian beam and ring beam.The phase holograms to be loaded on the SLM are calculated,and the complex amplitude manipulation procedure of light field is presented.After optimizing the relevant experimental parameters,we build up a beam shaping system for subsequent performance comparison among four complex amplitude manipulation methods.(3)We carry out performance comparison for different target light fields,in term of generation efficiency and intensity profile quality.We propose the peak signal-to-noise ratio(PSNR)from the image quality evaluation metric to compare the intensity distribution of the generated light field with ideal intensity distriubtion.Our experimental results indicate that four complex amplitude manipulation methods can successfully realize the function of beam shaping,with individual distinctive advantages and disadvantages.Among them,the Davis algorithm has high energy utilization while ensuring the quality of the light field,and it has great application value of beam shaping.